I am testing an industrial robot (ABB IRB 1410) using three simple Micron Dial gauges to get x,y,z values at particular point by varying Speed, Load and distance from home position. My questions are, Whether these three parameters influencing the repeatability or only the accuracy? Using dial gauges, without any relation to the Base frame, is it possible to measure accuracy? Is any other cost effective method to measure the repeatability and accuracy like above method?
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Without relation to the base frame, or to some physical point, absolute accuracy cannot be measured. You can measure repeatability via a dial gauge and any fixed point, but absolute accuracy will require careful measurements from wherever on the robot that 0,0,0 is referenced from. Repeatability requires only one point of reference, although you will get a better idea of over all performance if you use several points. But accuracy has to be a measurement between TWO points. One being a reference point - such as the base frame, and the other can be arbitrary. If you have a long accurate ruler,or rod of known length, this could be clamped into any arbitrary position, and the arm made to run from one end to the other, and then measure the offset from that. That would give you some idea of how accurate it is across the section of its reach, which would be probably pretty close to its absolute accuracy. Errors would be introduced by the rulers inaccuracys in length, and bend.
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$\begingroup$ Thank you. whether speed, load, distance are influential parameter on repeatability or not? $\endgroup$– Bhala RCommented Dec 29, 2013 at 15:55
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$\begingroup$ Load is the greatest modifier of repeatability if the load changes. The ABB models are normally calibrated without load, and the static load is compensated for in software. Dynamic load is harder to correct for. Speed affects dynamic load & inertia. Error should remain constant across distance. $\endgroup$– Mhz4.77Commented Dec 29, 2013 at 16:30
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$\begingroup$ @Mhz4.77 the arm full extended (more horizontal distance) with load, even with springs or other compensator, put I high change in load on the arm servo-motor, so that the error changes with distance? I don't calibrated nor programmed one of these, just thinking about. $\endgroup$ Commented Jan 2, 2014 at 18:35